I noticed I had more blank covers than not. I deleted all the ones with no cover in cover view. I set my preferences in Calibre, Output Options, Mobi, and UNchecked the box "enable sharing over facebook._ then I reconverted the books, plugged in the USB, and resent them to the Paperwhite. Now all the covers are there.
I thought I was following the directions I'd read here, but realized that I didn't have wifi on. So don't know if checking that box made a difference, or simply reconverting. See my next post.....I don't do it this way now.
Last edited by booklover6; 12-10-2012 at 06:39 AM.